Electronic shelves such as those found within the telecommunications industry, for example, provide a plurality of receiving stations for electronic circuit packs. Each circuit pack typically comprises a printed circuit board having a faceplate and a retaining latch arrangement on a forward portion of the printed circuit board and a connector element (male or female) disposed on a rear portion for mating with a corresponding connector element located within the receiving station. In recent years, the electronic industry has utilized connectors having significantly more terminal pins than in the past and in doing so has realized the need for accurate alignment of connector elements to prevent damage to the terminal pins during mating of the connector elements.
Connectors having in the range of 300 to 400 terminal pins are widely in use today. A mis-alignment of connector elements during insertion of a circuit pack into a respective receiving station can bend one or more terminal pins and render both the connector and the complete assembled circuit pack, unusable. Connector elements typically have a portion of each terminal pin soldered directly to a terminal on the printed circuit board and hence the freeing up of 300 to 400 soldered terminal pins of a damaged connector element is virtually impossible without damaging the printed circuit board as well. The expense associated with damaging a connector element to either a customer or the manufacturer is of such a magnitude that great effort has been made on the part of manufacturers to provide for mechanical alignment of the connector elements just prior to mating.
Mechanical alignment arrangements have been-used where one connector element incorporates a shroud structure which telescopically mates with an outer surface of a corresponding connector element to effectively align the mating connector elements immediately prior to electrical engagement. Some connector manufacturers provide the above telescopic mating structure as a primary alignment arrangement and provide an integral secondary alignment arrangement which typically comprises a cylindrical shaft which has a tapered tip and extends beyond the shroud of one connector element, and a guide orifice or channel of the other connector element for receiving the shaft prior to the primary alignment arrangement influencing the relative positions of the connector elements.
Keying, a function which permits only certain desired circuit packs to be received and electrically connected within a particular receiving station has been achieved by providing a pair of keying elements which are integral with the alignment arrangements. Manufacturers have, for example, conveniently associated one keying element with each element of the secondary connector alignment arrangements.
It has been found that in worst case tolerance situations the alignment arrangements and the keying elements can effectively work against each other, hence, making insertion of a printed circuit board into a receiving station more difficult than need be. The potential for misalignment of connector elements increases if due to poor tolerance situations, the keying elements (which mate prior to the connector elements), operate against true interaction of the alignment arrangements.